The invention relates to a portable apparatus for failure analysis or temperature characterization of packaged integrated circuit (I.C.) chips used in the semiconductor industry.
Failure analysis, which is a post-mortem examination of failed I.C. chips to determine the causes of failure, is an important procedure in semiconductor manufacturing. By using failure analysis, corrective actions may be taken in production processing, device design, test or application to eliminate the cause or prevent recurrence of the failure reported. Failure analysis typically consists of inserting a decapped I.C. chip into a test socket, subjecting the chip to extreme temperatures (in the range of about -60.degree. C. to +150.degree. C.) and performing electrical tests to determine (1) whether opens, shorts or abnormal characteristics exist between pairs of pins, pins and die or substrate, or pins and device package, (2) the threshold voltages of transistors, clock signals, and (3), in general, the operating characteristics of the I.C. chip. Testing is accomplished, typically, at an analytical probing test station with the aid of in-circuit probing equipment such as a micromanipulator which allows visual inspection of the individual circuits on a chip under high magnification (of up to 2000X) and probing of the circuits by means of tungsten probe tips.
Closely related to failure analysis is temperature characterization of the I.C. chip. This is an electrical verification procedure by which a newly designed chip, immediately after fabrication, is subjected to extremes of temperature to insure that the chip meets all the required electrical parameters.
Heating the I.C. chips to temperatures suitable for the above purposes was frequently accomplished in the prior art, by contacting the decapped I.C. chip with a resistance heater. By this technique, although the chip under test can be heated quickly, it takes an unduly long time to cool the chip thereby making failure analysis of each individual chip time-consuming and costly, particularly in a high-volume production environment.
A conventional method of cooling the I.C. chip to temperatures suitable for the above purposes is by mounting the I.C. chip to be tested in an expansion chamber and passing a liquified gas such as liquid carbon dioxide into the chamber. Due to absorption of heat from the chamber, the liquified gas vaporizes, thereby cooling the chip. Such processes, however, create vibrations of the I.C. chip and cause condensation of water vapor on the chip, both of which impair microprobing of the microcircuits on the I.C. chip.
Another conventional method of cooling I.C. chips is by contacting the chip with a chuck which is cooled by a refrigeration unit consisting of one or more heat exchangers using a refrigerant. This mode of cooling, thus, requires cumbersome and bulky refrigeration units.
In addition to these disadvantages of the prior art processes, there does not exist a simple, inexpensive, reliable and portable (i.e., small size and weight) apparatus which has the dual feature of rapidly heating and cooling the I.C. chip to the worst extremes of temperature.
Another prior art method of cooling/heating wafers and electronic components, rather than I.C. chips per se, is by means of a solid state thermoelectric module using the Peltier effect. The thermoelectric module consists of a number of Peltier couples, formed by joining p-doped and n-doped semiconductor elements, connected electrically in series and thermally in parallel by means of copper connecting strips. The couples are embedded between ceramic faceplates to electrically insulate the connecting strips from external surfaces. Passage of an electrical current through the module heats all Peltier couple junctions attached to one faceplate and cools all the junctions attached to the other faceplate thereby pumping heat from one faceplate to the other. One prior art method which uses the thermoelectric modules to cool an integrated circuit on a printed circuit board is illustrated in the publication by D. A. Zeskind entitled "Thermoelectric Heat Pumps Cool Packages Electronically," Electronics, July 31, 1980, pages 104-113.